Hide tanning process with salt of polymeric acid resinous condensate of organic-oxo and organic nitrogen compounds



;the. same bath or in separate. baths. sequence may also be reversed.

i Patented "Oct? 1 e g-" 1sec HIDE TANNING PROCESSIWITH SALT F POLY- MERI ACID RESINOUS CONDENSATE OF OR- AND ORGANIQ NITROGEN COM- .J iirgen Plapper and Ruth Heyden, Dusseldorf,'Germany, ass'ignors to Bohme FettchemieG;n1.b.H.;"Dusseldorf, Germany, a corporation or Germany No Drawing. Filed Aug. 2, 1955, Ser. No. 526,068

Claims priority, application'Germany Aug. 13, 1954 14 Ciaims.' (Cl. 894;33)

This invention relates to a tanning process, andmore particularly to a tanning process using insoluble neutral 1 derivatives of cation-active resins as'tanning agents.

It is well known that, when aqueous solutions of watersoluble, cationactive, nitrogen-containing resins are combined with aqueous solutions of salts of polymeric'inorganic or organicacids, virtually completely insoluble,

Y neutral, salt-like compounds are formed. These salt-like compounds very readily precipitate'from 'the solution and are stable in the presence of dilute acids and alkalies. We have found thatsuch insoluble resin derivatives, which may be regarded as salts, can be caused to *precipitate in the skin tissue of hides and furs, whereby a tanning effect isachieved. For this purpose, the hides or.

furs are first treated with a solution of water-soluble cationic resins and thereafter treated with alkali metal salts of polymeric inorganic or organic acids, either in However, this If the treatments are carried .out in' thesame. bath,

care must be taken that the component f first applied to the hides or furs has been substantially completelyabsorbed by the skin tissue before the other componentis slowly added to the bath invsmall por'tions,,-so .asto avoid an excess formation of precipitate outside the skin tissue.

The absorption of these salt-like polymericvacid resin derivatives by the skin tissue canbe improvedby reducing the pH of the solution to between 3.5"and '4.5. x

The process in .accordancewith. the .presentcinvention may also be carried out in the presence of;and in combination with other known tanning agents suchas formaldehyde, vegetable, synthetic and mineral tanningagents,

for example chromium and aluminum salts -andfatty tanning agents. Its combination with chrome-tanning agents is particularly suitable for the production of pump chrome-tanned leather.

The process herein described produces flawless, highgrade leather, regardless of whether it is applied tohides or furs as the sole tanning process, or whether his in combination with small amounts of other tanning agents. If the present process is used as an additional tanning treatment of leathers previously tanned with mineral tanning agents, the finished leather shows improved plumpness and possesses improved water-resistant characteristics. Moreover, since the salt-like resin derivatives deposited in the skin tissue are stable against attack by dilute acids and alkalies, leather tanned in'accordance with the present invention is unaffected by perspiration. Finally, the tanning Ieffect achieved thereby cannot be reversed with acid or alkaline media.

More specifically, the water-soluble salts of polymeric inorganic or organic acids,above referred to, are under stood to include the alkali metal salts of polymeric silicic acids, thealkali metal salts of polymeric phosphoric acids and the alkali metal salts of polymeric acrylic and meth- '2 acrylic. acids. ,Similarly, the ammonium salts Jand"'the salts. of organic. bases of "these polymeric acids-may be used.

' The term cation-active resins, above 'referred to; is

' intended to designate resinous compounds whichcontain one or more basic groups in the molecule which "render the total molecule, as such or in the form ofitssalts,

vsoluble in water. Such resinous compounds arewell known in industry. They may, for example, beprodueed by reacting oxo-compounds with organicnitrogen compounds containing amino or imino groups. 7 I

Organic nitrogen compounds which are capable of condensing with oxo-cornpounds to form cation-active resins for example, urea, thiourea," methylenediurea, cyanamide, guanidine, alkylguanidines, dicyandiarnide, dicyandiamidine, guanamine, ammeline, ammelide, melamine, and the like. v V s Examples of suitable oXo-compounds are. formaldehyde, acetaldehyde, acrolein, furfural, .rnethylethylketone .or compounds'which yield aliphatic aldehydes. H

- The resins formed by the reaction between the'oxocompounds and the organic nitrogen compounds," as

above indicated, often have inherent cation-actiyechar- -acteristics andtmay be transformed into wate r soluble salts with inorganic. or organic acids. They may, .however, also be imparted with more pronounced cationactive characteristics by condensing them with further 4 basic compoundsjfor example, with polyaminocompounds, suchas polyalkylenepolyamines, i.e. triethy'lenetetramine or tetraethyle'nepentamine, oxya'lkylamines, such as dimethylaminoethanol, diethanolamine; 'oxaz'olidines, polyphenyldiguanidines, andthe like.

, In addition to the specific resins recited abovefother known water-soluble cation active resins may also-be employed, in producing the salt-like neutral compounds usedfor tanning leather in accordance with-the present invention.

Ifv water glass solutions are-used as the salt of an inorganic polymeric acid, ittis preferred that'thewater glass contain a relatively low,Na O:SiO 'ratio,'.for example a ratio oftabout 1:3.8. Water glass solutionsf'are fgener'ally strongly alkaline and, beforethey-are brought into contact with raw hides or with .pre-tanned leather, they should slowly be adjusted to apH-value of between 3.5 and 4.5, for eXainple-with'an 8 to 10% aqueous acetic acid solution. The concentration of the water glass solution should not 'exceed about 2 to 3%. De-

pendinguponithe'thickness of the hide, 'a'period of from 1 to 4 hours is" required. to thoroughly impregnat a h hide with the water glass'solution. T Thereaften the hides or furs are slowly impregnatedwith a 3 to 10% solution of a cation-activeresin, either in a 'separate batli or by merely 'addingthe proper amount of resin to the waterglass' solution. I

' A much morerapid and improved tanningeflect can be achieved if thesequence of theabove describd-steps is reversed; i.e.,"if the hides or furs are fir'st' impregnated with the cation-active resin solution and then treated with ing to the present invention may beappliedasthesole tanning procedure, or in combination with a slight preliminary or subsequent chrome-tanning procedure using from 0.5 to 1% Cr O in the form of a commercial chrome-tanning agent. When plumping or impregnating already chrome-tanned leather, small amounts of cationactive resin and water glass may also be used.

If instead of water glass, polymeric phosphates are used with the watersoluble cation-active resins, the procedure is substantially the same as that described in the preceding paragraphs. Since the polymeric phosphates, for example hexametaphosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, and the like, are in most cases stable compounds and react either neutral or weakly acid, adjustment of the pH of the tanning solution with acetic acid, such as is necessary when using strongly alkaline water glass solutions, becomes superfluous, so that the tanning process is considerably simplified. Similarly, when using polymeric phosphates the concentration of the tanning solution has a lesser influence upon the stability and upon the capability of polyphosphate solutions to penetrate into the hide or leather.

When using polyphosphates, the amount of polyphosphate may vary between 2 and 10%, preferably between 4 and 5%, and the amount of water-soluble cation-active nitrogen-containing resin may vary between 2 and 12%, preferably between 6 and 8%, if the above-described tanning procedure is the sole tanning procedure applied to the hide or leather. When the tanning process according to the present invention is combined with other tanning processes using known tanning agents, or when it is desired to plump chrome-tanned leather, the amounts of both components may be reduced proportionately.

Additional tanning agents which may be used in combination with the tanning agents according to our invention include, in addition to the above-mentioned chrometanning agents, aluminum or zirconium salts, vegetable tanning agents or synthetic tanning agents of known composition, as well as fatty tanning agents, such as train oil, alkylsulfates, alkylsulfonates, alkylbenzenesulfonates and their corresponding sulfo-chlorides, and like compounds. The alkylsulfates, alkylbenzenesulfonates, etc., may also be used simultaneously with the salts of polymeric acids, whereby particularly soft leather is produced.

The following examples will further illustrate our invention and enable others skilled in the art to understand the invention more completely. It is to be understood, however, that our invention is not limited to these examples. The percentages in the examples below are based upon the pelt weight.

EXAMPLE I Plumping 0f chrome-tanned leather Chrome-tanned cowhides were rinsed for a short time and then, without being neutralized, treated for 1 to 2 hours with about 2% by weight of water glass (the ratio of Na O to SiO being about 123.8) in 2.5% aqueous solution. This solution had previously been adjusted to a pH-value between 4 and 4.5 with a 10% aqueous acetic acid solution. Thereafter, 4% of a cation-active resinous condensation product, produced from 0.5 mol dicyandiamide, 0.5 mol guanidinehydrochloride, and 3 mols formaldehyde, in 10% aqueous solution, were added to the acid water glass solution in small portions over a period of about 1 hour. When tanning the chrometanned leather in separate baths, the resin solution required was about the same as that of water glass solution.

The tanning procedure above described was also applied to chrome-tanned leather in the reverse order-that is, by first treating the leather with the cation-active resin solution and subsequently with a water glass solution in the following manner:

The chrome-tanned leather was first treated with a solution containing 100% water at 20 C. and 4% of the above-described cation-active resin product for about 1 to 2 hours. Thereafter, the leather was transferred to a separate bath containing 250% water at 20 C. and

EXAMPLE II Production of white leather Sheep pelts were first freed from lime and bated and thereafter immersed for 2 hours in a solution containing water at 20 C. and 4 to 5% of the water-soluble resinous condensation product described in Example I, or a similar amount of a condensation product formed by 1 mol melamine and 3 mols formaldehyde. Thereafter, the pelts were transferred to a tumbler containing about 100% water. The tumbler was then set in motion and a solution containing from 2 to 2.5% water glass in about water, which had previously been adjusted to a pH of 4 to 4.5 with acetic acid, was slowly added to the Water. After all of the solution was added, the pelts were allowed to remain in the tumbler for about 1 to 1 /2 hours. At the end of this period, the pelts were removed from the tumbler, placed on a trestle for about 24 hours, rinsed, fat-liquored and than finished in the customary manner. The resulting leather was virtually pure white and excellently suited for use as light uppers or for leather used in the manufacture of brief cases and the like.

As a variation, the above process was modified with a moderate subsequent chrome-tanning procedure, using from 0.5 to 1% Cr O in the usual manner. Depending upon the amount of chromium used, the resulting leather ranged from pure white to lightly colored.

EXAMPLE III Production 0) white leather Calf hides which had previously been limed, washed to remove excess lime, and bated, were immersed for about 2 hours in a solution containing about 100% water at 20 C. and 3 to 5% of a cation-active resinous condensation product produced either from 0.5 mol dicyandiamide, 0.5 mol guanidinehydrochloride and 3 mols formaldehyde, or 1 mol dicyandiamide and 5 mols formaldehyde. Thereafter, the hides were trestled overnight and then immersed for about 2 hours in a new bath containing 100% water and 6 to 10% hexametaphosphate. Subsequently, the hides were subjected to an after-treatment either in the same bath or in a separate bath with 3 to 5% of one of the above cation-active, nitrogen-containing resinous condensation products in 10% aqueous solution. If this after-treatment is carried out in the hexametaphosphate bath, the addition of cation-active resins must be completed within a period of about 1 hour. After tanning the hides in this manner, they were again trestled for a short period of time, rinsed, fat-liquored and finally finished in the customary fashion. The leather thus obtained had a pliability and feel similar to upper leather, and was excellently adapted for the production of suede.

EXAMPLE IV Tanning process in combination with chrome-tanning Calf or goat hides, which had been freed from excess lime and bated, were pickled for about 10 minutes with a solution containing 100% water at 20 C., 6% sodium chloride and 0.8% sulfuric acid. Thereafter, 2 to 3% of the cation-active resin condensation product described in Example I were added to the pickling solution, and the hides were allowed to remain therein for about 1 /2 hours. Subsequently, the hides were transferred to a separate bath comprising 80% Water at 20 C., 3% sodium chloride and 0.5% Cr O (commercial chrome-tanning agent) .and allowed to remain in this bath for about 3 hours without neutralization. At the end of this period, the hides were removed from the bath, placed on a trestle overnight, and then immersed for about 1 hour in a solution containing 100% water at 20 C. and 3 to 5% hexametaphosphate. Thereafter, the hides were treated with 2 to 3% of the cationic resin condensation product of Example I, either in the same bath or a separate bath. After a short period of trestling and rinsing, the tanned hides were finished in the customary manner. The resulting leather was excellently suited for use as uppers.

EXAMPLE V Plumping of chrome-tanned leather Chrome-tanned leather was neutralized and then immersed for about 1 /2 hours in a solution containing 100% water and 3 to 4% hexametaphosphate. Thereafter, the leather was transferred to a separate bath containing 100% water and 4 to 6% of cation-active, watersoluble resin produced from 1 mol guanylureahydrochloride and 5.3 mols formaldehyde. The resulting leather had a very plump and pleasant feel.

While we have given certain specific embodiments of our invention, we wish it to be understood that the invention is not limited to such embodiments and that various changes and modifications may be made therein without departing from the spirit of our invention or the scope of the appended claims.

We claim:

1. The method of tanning animal hides which comprises contacting said hides sequentially with aqueous solutions of water-soluble salts of a polymeric acid selected from the group consisting of polymeric silicic acid and polymeric phosphoric acid and 'with aqueous solutions of water-soluble cation-active resinous compounds formed by condensing an organic oxocompound selected from the group consisting of formaldehyde, acetaldehyde, acrolein, furfural and methylethylketone with an organic nitrogen compound selected from the group consisting of urea, thiourea, methylenediurea, cyanamide, guanidine, alkylguanidines, dicyandiamide, dicyandiamidine, guanamine, ammeline, ammelide and melamine, at a pH of between about 3.5 to about 4.5.

2. The method of tanning animal hides which comprises contacting said hides sequentially with aqueous solutions of water-soluble salts of a polymeric acid selected from the group consisting of polymeric silicic acid and polymeric phosphoric acid, and with aqueous solutions of water-soluble cation-active resinous compounds formed by condensing an organic oxocompound selected from the group consisting of formaldehyde, acetaldehyde, acrolein, furfural and methylethylketone with an organic nitrogen compound selected from the group consisting of urea, thiourea, methylenediurea, cyanamide, guanidine, alkylguanidines, dicyandiamide, dicyandiamidine, guanamine, ammeline, ammelide and melamine, at a pH of between about 3.5 to about 4.5, wherein the first solution applied is permitted to be substantially completely absorbed by the skin before the second solution is applied.

3. The method of tanning animal hides as in claim 1, which comprises, in addition, tanning such hides with a customary tanning agent selected from the group consisting of formaldehyde, vegetable, synthetic, mineral and fatty tanning agents.

4. The method of tanning animal hides as in claim 3, wherein said fatty tanning agent is a fatty alkylsulfate containing high molecular alkyl radicals of at least 8 carbon atoms.

5. The method of tanning animal hides as in claim 1, which comprises, in addition, tanning said hides with a chromium oxide tanning agent prior to contacting said hides with said aqueous solutions.

6. The method of tanning animal hides as in claim 1, wherein a portion of said water-soluble salts of polymeric acids are substituted by anion-active fatty tanning agents.

7. The method of claim 1 wherein the water-soluble salt of the polymeric acid is a salt selected from the group consisting of a potassium salt, an ammonium salt and an organic base salt.

8. The method of tanning animal hides as in claim 3, wherein said fatty tanning agent is a fatty alkylsulfonate containing high molecular alkyl radicals of at least 8 carbon atoms.

9. The method of tanning animal hides as in claim 3, wherein said fatty tanning agent is a fatty alkylbenzenesulfonate containing high molecular alkyl radical of at least 8 carbon atoms.

10. The method of tanning animal hides which comprises contacting said hides sequentially with a water glass solution and an aqueous solution of a cation-active resinous condensation product of dicyandiamide, guanidinehydrochloride and formaldehyde, at a pH of 3.5 to 4.5.

11. The method of tanning animal hides which comprises contacting said hides sequentially with a water glass solution and an aqueous solution of a cation-active resinous condensation product of melamine and formaldehyde, at apH of 3.5 to 4.5.

12. The method of tanning animal hides which comprises contacting said hides sequentially with an aqueous hexametaphosphate solution and an aqueous solution of a cation-active resinous condensation product of dicyandiamide and formaldehyde, at a pH of 3.5 to 4.5.

13. The method of tanning animal hides which comprises contacting said hides sequentially with an aqueous hexametaphosphate solution and an aqueous solution of a cation-active resinous condensation product of dicyandiamide, guanidinehydrochloride and formaldehyde, at a pH of 3.5 to 4.5.

14. The method of tanning animal hides which comprises contacting said hides sequentially with an aqueous hexametaphosphate solution and an aqueous solution of a cation-active resinous condensation product of guanylureahydrochloride and formaldehyde, at a pH of 3.5 to 4.5.

References Cited in the file of this patent UNITED STATES PATENTS 2,218,582 Linder Oct. 22, 1940 2,290,294 Riess et al. July 21, 1942 2,328,901 Grimm et al Sept. 7, 1943 2,621,102 Nagy Dec. 9, 1952 2,637,622 Dawson et al. May 5, 1953 2,663,614 Haag Dec. 22, 1953 2,809,088 Meister et al Oct. 8, 1957 FOREIGN PATENTS 530,643 Great Britain Dec. 17, 1940 OTHER REFERENCES Chen: Syntans and Newer Methods of Tanning, The Chem. Elements Publ., So. Lancaster, Mass, 1950, pp. 82-86. 

1. THE METHOD OF TANNING ANIMAL HIDES WHICH COMPRISES CONTACTING SAID HIDES SEQUENTIALLY WITH AQUEOUS SOLUTIONS OF WATER-SOLUBLE SALTS OF A POLYMERIC SILICIC ACID AND FROM THE GROUP CONSISTING OF POLYMERIC SILICIC ACID AND POLYMERIC PHOSPHORIC ACID AND WITH AQUEOUS SOLUTINS OF WATER-SOLUBLE CATION-ACTIVE RESINOUS COMPOUNDS FORMED BY CONDENSING AN ORGANIC OXO-COMPOUND SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, ACETALDEHYDE, ACROLEIN, FURFURAL AND METHYLETHYLKETONE WITH AN ORGANIC NITROGEN COMPOUND SELECTED FROM THE GROUP CONSISTING OF UREA, THIOUREA, METHYLENEDIUREA, CYANAMIDE, GUANIDIENE, ALKYLGUANIDINES, DICYANDIAMIDE, DICYANDIAMIDE, GUANAMINE, AMMELINE, AMMELIDE AND MELAMINE, AT A PH OF BETWEEN ABOUT 3.5 TO ABOUT 4.5. 